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Abstract:

Measurement points for display on a two-dimensional pixel-based display
device are formed by scanned and digitized measurement values. To this
end, the resolution of each measurement point according to time and/or
value is higher than the resolution of the two-dimensional pixel-based
display device. The measurement points are connected into a continuous
measurement point curve if they are not located on directly adjoining
pixels. In order to determine the pixels to be depicted of the continuous
measurement point curve between two measurement points not located on
directly adjoining pixels, the positions of the adjoining measurement
points within the associated pixels are taken into consideration.

2. The method according to claim 1, characterized in that, in order to
determine the pixels of the continuous measurement-point curve (30, 31,
32, 60, 61, 62) between two adjacent measurement points (13, 21, 22, 23,
33, 34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) to be displayed,
which are horizontally offset, one or more transition points of the
continuous measurement-point curve (30, 31, 32, 60, 61, 62) are
calculated across the boundaries between the pixel rows (15), that the
continuous measurement-point curve (30, 31, 32, 60, 61, 62) from the
first of the two adjacent measurement points (13, 21, 22, 23, 33, 34, 50,
51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) to the first transition point
in the pixel row (15) of the first measurement point (13, 21, 22, 23, 33,
34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) is displayed, that
the continuous measurement-point curve (30, 31, 32, 60, 61, 62) from the
first transition point to the last transition point in the respectively
exceeded pixel row (15) is displayed and that the continuous
measurement-point curve (30, 31, 32, 60, 61, 62) is displayed from the
last transition point to the second of the two adjacent measurement
points (13, 21, 22, 23, 33, 34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75,
76, 77) in the pixel row (15) of the second measurement point (13, 21,
22, 23, 33, 34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77).

3. The method according to claim 1 or 2, characterized in that, in order
to determine the pixels of the continuous measurement-point curve (30,
31, 32, 60, 61, 62) between two adjacent measurement points (13, 21, 22,
23, 33, 34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) to be
displayed, which are vertically offset, one or more transition points of
the continuous measurement-point curve (30, 31, 32, 60, 61, 62) are
calculated across the boundaries between the pixel columns (14), that the
continuous measurement-point curve (30, 31, 32, 60, 61, 62) from the
first of the two adjacent measurement points (13, 21, 22, 23, 33, 34, 50,
51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) to the first transition point
in the pixel column (14) of the first measurement point (13, 21, 22, 23,
33, 34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) is displayed,
that the continuous measurement-point curve (30, 31, 32, 60, 61, 62) from
the first transition point to the last transition point in the
respectively exceeded pixel column (14) is displayed, and that the
continuous measurement-point curve (30, 31, 32, 60, 61, 62) from the last
transition point to the second of the two adjacent measurement points
(13, 21, 22, 23, 33, 34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77)
in the pixel column (14) of the second measurement point (13, 21, 22, 23,
33, 34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) is displayed.

4. The method according to claim 2 or 3, characterized in that the
transition point or respectively the transition points is calculated from
the proportions of the length of a direct connecting line of the two
measurement points (13, 21, 22, 23, 33, 34, 50, 51, 52, 63, 64, 65, 66,
67, 68, 75, 76, 77) extending in the pixel columns (14) or respectively
pixel rows (15).

5. The method according to any one of claims 1 to 4, characterized in
that the two adjacent measurement points (13, 21, 22, 23, 33, 34, 50, 51,
52, 63, 64, 65, 66, 67, 68, 75, 76, 77) to be connected to form a
continuous measurement-point curve (30, 31, 32, 60, 61, 62) are offset
horizontally or vertically by precisely one pixel column (14) or
respectively pixel row (15).

6. The method according to any one of claims 1 to 5, characterized in
that all pixels exceeded by a direct connecting line of the two
measurement points (13, 21, 22, 23, 33, 34, 50, 51, 52, 63, 64, 65, 66,
67, 68, 75, 76, 77) to be connected are displayed as part of the
continuous measurement-point curve (30, 31, 32, 60, 61, 62).

10. The device according to claim 8 or 9, characterized in that the
pixel-connecting device (102) calculates the transition point or
respectively the transition points from the proportions of the length of
a direct connecting line of the two measurement points (13, 21, 22, 23,
33, 34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) extending in the
pixel columns (14) or respectively pixel rows (15).

11. The device according to any one of claims 7 to 10, characterized in
that the two adjacent measurement points (13, 21, 22, 23, 33, 34, 50, 51,
52, 63, 64, 65, 66, 67, 68, 75, 76, 77) to be connected to form a
continuous measurement-point curve (30, 31, 32, 60, 61, 62) are offset
horizontally or vertically by precisely one pixel column (14) or
respectively pixel row (15).

12. The device according to any one of claims 7 to 11, characterized in
that the pixel-connecting device (102) specifies all pixels exceeded by a
direct connecting line of the two measurement points (13, 21, 22, 23, 33,
34, 50, 51, 52, 63, 64, 65, 66, 67, 68, 75, 76, 77) to be connected as
part of the continuous measurement-point curve (30, 31, 32, 60, 61, 62).

Description:

[0001] The invention relates to a method and a device for displaying
digital measurement values on pixel-based display devices, in particular,
display devices in measuring devices.

[0002] For the display of digital measurement values on pixel-based
displays, the measurement values are conventionally imaged as precisely
as possible onto individual pixels. However, if the measurement values
are disposed far apart, an image of poor legibility, which only consists
of individual points, is obtained. For this reason, an interpolation
between the measurement values is conventionally implemented. This
produces a more readily legible image, but is associated with high
calculation costs. However, if the sampling times of the digital signal
are not synchronized with the image change of the display, an unstable
image is also obtained with this method, because different measurement
curves result from the different interpolation points of the
interpolation.

[0003] Accordingly, a method and a device for the presentation of
waveforms are disclosed in EP 0 919 818 B1. The method uses an
interpolation of displayed points between measurement values. On one
hand, this requires a high calculation cost. On the other hand, a stable
image is not always produced, since the position of the interpolation
points of the interpolation varies because of lack of synchronicity of
the sampling times with the structuring of the image.

[0004] The invention is based upon the object of providing a method and a
device, which present digital measurement values on a display with a
stable image, good legibility and low calculation costs.

[0005] This object is achieved for the method according to the invention
by the features of the independent claim 1 and for the device by the
features of the independent claim 7. Advantageous further developments
form the subject matter of the dependent claims relating back to these
claims.

[0006] For the display of measurement values on a two-dimensional
pixel-based display device, measurement points in a two-dimensional
coordinate system are formed from sampled and digitized measurement
values. In this context, the resolution of each measurement point
according to time and/or value is higher than the resolution of the
two-dimensional, pixel-based display. The measurement points are
connected to form a continuous measurement-point curve, if they are not
disposed on directly adjacent pixels. To determine the pixels of the
continuous measurement-point curve between two measurement points to be
displayed, which are not disposed on directly adjacent pixels, the
position of the adjacent measurement points within the associated pixels
is taken into consideration. The continuous measurement-point curve
displayed becomes clearer as a result and, over the time course of the
measurement with a constant signal, is more stable than with conventional
display methods.

[0007] To determine the pixels of the continuous measurement-point curve
between two adjacent measurement points to be displayed, which are
horizontally offset by precisely one pixel, one or more transition points
of the continuous measurement-point curve are preferably calculated
across the boundaries between the pixel rows. The continuous
measurement-point curve from the first of the two adjacent measurement
points to the first transition point is advantageously displayed in the
pixel row of the first measurement point. The continuous
measurement-point curve from the first transition point to the last
transition point is advantageously displayed in each case in the scanned
pixel row. The continuous measurement-point curve from the last
transition point to the second of the two adjacent measurement points is
advantageously displayed in the pixel row of the second measurement
point.

[0008] To determine the pixels of the continuous measurement-point curve
between two adjacent measurement points to be displayed, which are
vertically offset, a transition point of the continuous measurement-point
curve is preferably calculated across the boundaries between the pixel
columns. The continuous measurement-point curve from the first of the two
adjacent measurement points to the first transition point is
advantageously displayed in the pixel column of the first measurement
point. The continuous measurement-point curve from the first transition
point to the last transition point is advantageously displayed in each
case in the scanned pixel column. The continuous measurement-point curve
from the last transition point to the second of the two adjacent
measurement points is advantageously displayed in the pixel column of the
second measurement point. Accordingly, it is unambiguously specified how
the measurement-point curve is to be displayed. An unambiguous, clear and
at the same time stable curve, which largely corresponds to the
characteristic of the analog measurement value is obtained.

[0009] The transition point or points are preferably calculated from the
proportions of the length of a direct connecting line of the two
measurement points extending in the pixel columns or respectively the
pixel rows. With a curve obtained in this manner, the proximity to the
analog measurement values can be further increased.

[0010] The two adjacent measurement points to be connected to form a
continuous measurement-point curve are advantageously horizontally or
vertically offset by precisely one pixel column or respectively pixel
row.

[0011] As an alternative, all pixels exceeded by a direct connecting line
of the two measurement points to be connected are displayed as a part of
the continuous measurement-point curve. As a result of this alternative
method, a sufficiently stable and clear curve is achieved with a very low
calculation cost.

[0012] The invention is described by way of example with reference to the
drawings, in which an advantageous exemplary embodiment of the invention
is illustrated. The drawings are as follows:

[0013] FIG. 1 shows the characteristic of a first exemplary, analog signal
and of the associated sampled signal;

[0014]FIG. 2 shows the characteristic of a second exemplary, analog
signal and of the associated sampled signal in several sampling runs;

[0017]FIG. 5 shows a first exemplary analog signal superimposed over
associated measurement points of several sampling runs on a
two-dimensional display device;

[0018]FIG. 6 shows a first exemplary output of a two-dimensional display
device resulting from the signal from FIG. 5;

[0019]FIG. 7 shows exemplary signals with connections according to the
invention of measurement points on a two-dimensional display device;

[0020]FIG. 8 shows a second exemplary analog signal superimposed over
associated measurement points of several sampling runs on a
two-dimensional display device;

[0021]FIG. 9 shows a second exemplary output of a two-dimensional display
device here resulting from the signal from FIG. 8; and

[0022]FIG. 10 shows a block-circuit diagram of an exemplary embodiment of
the device according to the invention.

[0023] Initially, the problem and the signals occurring are explained with
reference to FIGS. 1-6. The functioning of an exemplary embodiment of the
method according to the invention is visualized with reference to FIGS. 7
and 9. On the basis of FIG. 10, the functioning of the device according
to the invention is explained. In some cases, a repetition of the
presentation and description of identical elements in similar drawings
has not been provided.

[0024] The following table provides a summary of the formula characters
used below.

TABLE-US-00001
Abbreviation Description
fa Sampling rate
NLine(k) Length of the line between the k-th and the
k + 1-th point
NLine, 1(k), Partial lines
NLine, 2(k)
NS--PX Sample number per column
NPX Number of pixel columns on the screen
SPX(k) Image column of the k-th point
TDisplay Time on the whole screen
TPX Time per pixel column
TS Time interval between two samples
tS(k) Time of the k-th sample
TTrigger Triggering time

[0025] In FIG. 1, the characteristic of a first exemplary analog and
sampled signal is presented. Let an analog measurement curve be given.
This can initially extend horizontally and then ascend and then extend
horizontally again. To record this measurement curve 12, let a trigger
threshold be defined. Let the timing point TTrigger 10, at which the
analog measurement curve 12 exceeds the trigger threshold 11, be selected
in the following section as a reference point for the display. The
display is realized on a two-dimensional, pixel-based display device,
which is subdivided into pixel columns 14 and pixel rows 15. The
measurement curve 12 is sampled. The sampled points 17 are disposed on
the measurement curve 12 in the display. To simplify the following
description, let it be assumed that the measurement curve 12 is only to
be displayed on the screen from the triggering time TTrigger 10. For
this purpose, a new time axis is defined, wherein the triggering time 10
represents the zero point. In general, the image display could also begin
at a random time before or after the triggering time TTrigger 10.

[0026] Since triggering and sampling are independent of one another, the
first sampled value is not generally disposed exactly at the triggering
time, but is offset in time by the trigger offset TTO 16.

[0027] Let fa be the sampling rate, then

TS=1/fa (1)

is the interval between two sampled values 13. The first sampled value 13
is then disposed after the triggering event randomly within the range

0≦TTO<TS (2)

[0028] If this first sampled value 13 has the index k=0, then the k-th
sampled value 13 is disposed at the time tS(k) with

tS(k)=kTS+TTO (3)

[0029] If a time

TDisplay (4)

is displayed on the whole screen, with NPX pixel columns 14, a time
TPX per pixel column 14 is calculated as

TPX=TDisplay/NPX. (5)

[0030] A sample xS(k) is displayed in the m-th pixel column 14, if

mTPX≦kTS(k)+TTO<(m+1)TPX with
0≦m≦NPX-1 (6)

applies. This equation can also be reformulated as follows:

S PX ( k ) = floor { k T S ( k ) + T TO
T PX } , ( 7 ) ##EQU00001##

wherein SPX(k) indicates the pixel column 14, to which the k-th
sample is assigned. The function floor rounds off the argument. This
results in an average sample number NSPX per column of

N S _ PX = T Display T S N PX . ( 8 )
##EQU00002##

[0031] By way of example: if

fa=1 GHz, (9)

it follows that

TS=1/fa=1 n sec. (10)

[0032] If the screen has NPX=1000 columns and if a time of
TDisplay=20 μs is displayed, the following results:

TPX=TDisplay/NPX=20 μsec/1000=2 n sec (11)

and furthermore

N S _ PX = 20 μ sec 1 n sec
1000 = 2. ( 12 ) ##EQU00003##

[0033] By analogy, for

fa=0.5 GHz, (13),

the following applies

N S _ PX = 20 μ sec 2 n
sec 1000 = 1. ( 14 ) ##EQU00004##

[0034]FIG. 2 shows the characteristic of a second exemplary analog and
sampled signal 20 in several sampling runs. In this context, the sampled
points 21, 22, 23 correspond to three different sampling runs. The
distance between sampled points 21, 22, 23 of the same sampling run is
greater than the distance between the pixel rows. Accordingly, pixels, in
which no sampled points occur, are disposed between the sampled points.

[0035] The simplest display mode is the so-called point mode: only the
sampled values are presented on the screen as points. If only one
measurement curve and a small NS--PX is available, that is
to say, a few points per pixel column, only individual points are shown
on screen. In order to show a continuous curve on the screen in point
mode, the following conditions are necessary:

[0036] either NS--PX must be selected to be sufficiently
large, which is not always possible,

[0037] or, in the case of a periodic signal, several measurement curves
must be superimposed. Since the trigger offset varies in a random manner,
a continuous curve is obtained.

[0038] In general, the brightness of a pixel on the screen is proportional
to the frequency of how often this image point has been "hit".

[0039] Another mode is the linear mode; in this mode, in each case, two
sampled values k and k+1 following one another in time succession are
connected by a line in the screen display. In the case of current
measuring devices, if these two points are not disposed in the same
screen column, three different methods are used for the line display. In
FIG. 3, exemplary connecting options for measurement points on a
two-dimensional display device are illustrated. A first option is that
the line 30 extends completely within the column of the measurement point
k 33. A further option is that the line 31 extends completely in the
column of the measurement point k+1 34. A final option is that half of
the line 32 extends in the column of measurement point k 33 and half in
the column of measurement point k+1 34.

[0040] The disadvantages of these illustrated methods are that the line
does not reflect the actual characteristic of the measured curve. This
applies in particular, if the line is drawn completely in the column of
measurement point k 33 or of measurement point k+1 34.

[0041] FIG. 4 shows these exemplary connecting options for measurement
points on a two-dimensional display device with superimposed, possible,
associated analog signal characteristics. Accordingly, the line 30 is
displayed completely in the column of measurement point 33. This provides
a good reflection of the possible characteristic 40 of the analog signal.
However, as in the case of measurement points 33 and 34, analog signals
41 and 42 are only poorly imaged. Artefacts are formed. Pixels are
displayed, which are not passed by the actual analog signal. Similar
considerations apply for the linear characteristic 31 and the possible
analog signals 44, 45, 46. The linear characteristic 32 achieves better
results with the possible analog signals 46, 47, 48, but also fails to
provide an optimum for all possible analog signals.

[0042] In FIG. 5, a first exemplary analog signal 53 is superimposed over
associated measurement points 50, 51, 52 of several sampling runs on a
two-dimensional display device. Let a measurement curve 53 have a
gradient of five pixel rows 15 per pixel column 14 and let the sampling
be implemented once per pixel column 14, that is to say,
NS--PX=1. Let this periodic measurement curve 53 be
sampled and recorded five times--each time with a slight time offset. Let
these sampled points 50, 51, 52 be marked in the image with X; those of
the first sampling are marked with a circle. Here, the connecting line is
drawn completely within the column of the measurement point k 33. The
connection with the following measurement point of the same sampling run
is drawn in for every measurement point.

[0043]FIG. 6 shows a first exemplary output of a two-dimensional display
device resulting from the signal from FIG. 5. The artefacts explained
with reference to FIG. 4 are displayed here. If the pixel frequencies are
displayed on screen as brightnesses 54, 55, 56, 57, 58, the display is
blurred by the drawing of the line on screen.

[0044] In FIG. 7, exemplary signals with connections according to the
invention between measurement points on a two-dimensional display device
are presented. Let NLine(k) be the length of the line between the
k-th point 63, 66, 68, which occurs in the pixel column SPX(k)=m 14,
and the k+1-th point 64, 65, 67, which occurs in the pixel column
SPX(k+1)=m+1 14. The line 60, 61, 62 is then drawn across two
columns. For the subdivision of the line 60, 61, 62 in the two columns,
the following relationship applies, wherein NLine,1(k) is the length
of the line 60, 61, 62 in the column m and NLine,2(k) is the length
of the line 60, 61, 62 in the column m+1:

[0046] Δt1(k) is the time interval of the k-th point 63, 66, 68
at the start of the next image column m+1, while Δt2(k)
indicates how far the k+1-th point 64, 65, 67 is already disposed in the
column m+1. If equation (15) is reformulated using equation (16), the
following is obtained

[0047] Accordingly, it is evident that with the measurement points 63 and
64, which are both disposed at the left-hand edge of their respective
pixel column 14, the connecting line 60 extends completely within the
pixel column 14 of measurement point 63. In the case of measurement
points 65, 66 disposed centrally in the pixels, the connecting line 61
extends in equal portions within the pixel columns 14 of measurement
points 65, 66. The measurement points 67, 68 are both disposed at the
right-hand edge of their respective pixel column 14. Accordingly, the
connecting line 62 extends completely within the pixel column 14 of
measurement point 67. The characteristic of the curve for every
measurement-point distribution is therefore reflected in an optimum
manner within the pixel. Furthermore, the artefacts, as seen in the
example from FIG. 6, do not occur.

[0048]FIG. 8 shows a second exemplary analog signal 73 superimposed over
associated measurement points 70, 71, 72 of several sampling runs on a
two-dimensional display device with pixel column 14 and pixel rows 15. By
contrast with FIG. 5, the connecting lines between the measurement points
70, 71, 72 here are orientated very much more strongly to the
characteristic of the analog signal 73. Only pixels, which are exceeded
by the analog signal 73, are touched by the connecting lines.

[0049] In FIG. 9, a second exemplary output 74 of a two-dimensional
display device, resulting here from the signal 73 from FIG. 8, is
illustrated. Since the frequency of the exceeding of each of the pixels,
which touch the connecting lines of the measurement points 70, 71, 72, is
identical, there is no blurring of the resulting curve. The curve 74 is
continuous, clear and adapted in an optimal manner to the analog signal
73.

[0050] Accordingly, with the method according to the invention, no
artefacts occur. By contrast, with a conventional linear interpolation
with NInterpolation interpolation points, artefacts can occur under
the following conditions:

[0051] if the number of interpolation points NInterpolation is
selected too low relative to the current line length N(k)Line, for
example, 10 interpolation points, while the vertical distance between two
image points is 200 lines, then only one point in every 20th line is set.
If these 10 interpolation points are connected, artefacts once again
occur.

[0052] if the number of interpolation points NInterpolation is
selected to be large, for example, 100 interpolation points, while the
vertical distance between two image points is 10 lines, considerable,
superfluous calculation costs are incurred.

[0053] moreover, with a fixed number of NInterpolation interpolation
points, a further artefact is provided: for example, if
NInterpolation 100, then every linear point with N(k)Line=10 is
set a total of 10 times and appears considerably brighter, than if the
line were to have a length of N(k)Line=100, wherein each image point
is set only once.

[0054] In FIG. 10, a block-circuit diagram of an exemplary embodiment of
the device according to the invention is illustrated. The sampled,
digitized measurement values 104 are transmitted to a scaling device 100.
This scales the measurement values 104 in such a manner that they can be
displayed on the display device 103. The scaled measurement values 105
are re-routed to the pixel-assignment device 101. This assigns the
measurement value pixels to the display device 103. The pixel-connecting
device 102 generates the continuous measurement-point curve, if the
pixels assigned by the pixel-assignment device 101 are not directly
adjacent. The display device 103 displays the continuous
measurement-value curve, which was generated by the pixel-connecting
device 102.

[0055] The invention is not restricted to the exemplary embodiment
presented. As already mentioned, both horizontal and also vertical
transitions of the measurement-point curve can be processed across the
pixel rows or respectively columns. Similarly, the use of the method in
three-dimensional, pixel-based displays is conceivable. All the features
described above or illustrated in the diagrams can be combined with one
another as required within the framework of the invention.